Tie the Knot
by nightday4647
Summary: Alpha Rei has always been uncomfortable with his status and the instincts that go along with it. So what is he to do when Nagisa presents himself as an omega when they are home alone? Reigisa basically pwp.


**This is a fill for the Free! Kink meme requesting Reigisa apha/omega heat sex and I was more than happy to oblige. There will be one more chapter to this story which I hope to have up in the next few days.**

**This fic does contain knotting so if that's not your thing then I would highly suggest you avert your eyes. **

**I don't own Free! or any of the characters. **

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Rei had the constant feeling that he was born into the wrong body. He knew he was an alpha and could constantly feel slightly aggressive urges hiding just beneath his skin, but he couldn't help but feel like he was the wrong person for the job. His life would be much easier if he had been born a beta like Nagisa. He would've even felt more comfortable as a docile omega if it meant he didn't have to feel the constant pressure to succeed or suppress his ugly alpha urges. His parents always assured him that he was in fact an alpha and meant to be one as well, but he didn't quite trust their judgment. Alphas were known to be strong, aggressive leaders, always ready to fight for the things they wanted. They sought omegas out and usually had at least a few loyal betas following them around. Rei didn't have any of that, didn't want it.

He didn't bring his insecurities about being a poor alpha up often but when he did he was always met with weird looks and a careful sniff in his direction. A firm "But you smell like an alpha," usually followed except when he asked Nagisa. Then he was met with a warm body pressing up against his and groping hands. "But look at all of these muscles Rei-chan! If you were a beta, you wouldn't be nearly this strong. I mean look at me! You're way stronger than I am."

Rei always replied with a small scoff and pushed the much smaller body away from his. "Haruka-senpai is stronger than you and he's an omega. I don't think you're the best role model for betas Nagisa-kun."

"Rei-chan is so cold," Nagisa would say with a pout before quickly bouncing back to his bubbly self and proceeding to climb all over Rei.

Rei thought that his words might comfort him some, but they always just left him feeling uneasy.

He often watched Makoto when he thought no one was looking, trying to copy his mannerisms and leadership qualities. Makoto was the alpha he had always inspired to be like. Many of the alphas that he had seen were fierce, instinct driven things prone to fighting amongst each other and intimidating betas, but Makoto was different. He was attentive to others needs and he'd never seen Makoto so much as raise his voice to Nagisa, let alone try to intimidate him. He cared about his makeshift pack greatly. While Rei often felt that he was as much Makoto's beta as Nagisa, he couldn't help but feel that maybe he was like Makoto. Not like all of the other violent alphas that Rei was frightened of, but one able to be a great leader without having to be violent, using kind words and heartfelt gestures instead.

He brought this up with Nagisa in a fleeting conversation on the train one evening after swim practice. "Makoto is a weird alpha," he mused. "He never acts violent at all."

"Hmm, does he not?" Nagisa replied questioningly. "You just think that because you didn't know what he was like before he had Haru-chan."

Rei tilted his head to the side. "Hasn't he always had Haruka-senpai? They've known each other since they were little."

Nagisa let out a peel of laughter before smacking Rei lightly on the shoulder. "Yes silly, I was talking about before they you know, tied the knot."

Rei felt his face turn the same shade as the frame of his glasses at such vulgar phrase. Nagisa may look cute and innocent, but Rei was convinced that he was a sex demon sent to torture him. Never the less he coughed lightly and prompted his friend to continue.

"Well Mako-chan has never been particularly violent I guess, but he isn't called a killer whale for nothing. I once saw him almost kill a guy for making fun of Haru-chan's girly name. He's never gotten into too many fights, but the ones he has gotten into have been bloody. He calmed down a lot though once he got Haru-chan as his omega."

Rei's mood plummeted with the news. _So even Makoto-senpai was an average alpha, or had been before he took a mate. Am I the only one who can't stand all the violence and lust?_

Rei was quiet for the rest of the train ride, and for once, Nagisa didn't bother him.

Once home, Rei contemplated this new information. _Maybe my instincts will be easier to control if I take a mate as well, _he thought to himself. He remembered how Rin had been when he first met him. He was the poster boy for alphas everywhere, violent, ill-tempered, and determined. However after the tournament, he had mellowed down and actually became a halfway decent guy. Still quick to anger but not as quick and much more forgiving than he used to be. He thought it was because he had finally been reunited with his childhood pack, but it might have been because he could finally see past his goal and take Nitori as his mate. Maybe an omega could solve everything.

But the more Rei thought about it, the more nauseous he became.

To him, omegas were off limits.

Rei wouldn't say that he had always been a poor example of an alpha. When he was in middle school and everyone began presenting, he was proud when he presented as an alpha. He got into a few scuffles, thought mostly verbal, with his alpha classmates, but life for the most part went on as usual. Being an alpha didn't interfere with his school work and he didn't really think differently from before he presented. To him being an alpha was great. He was always the leader of his group projects so he knew that they would get done satisfactorily and the teachers were much more lenient on his mildly violent outbursts.

However his entire view on the world changed one day when he was sent to the nurse's office because he had twisted his ankle while walking to class. He limped forward, hoping for his wound to start healing quickly as he made his way down the hall. Suddenly the most delicious scent in the world filled his nose, filled his entire being. It was mouthwatering in his intensity and he felt himself pulled toward it through no will of his own. His ankle didn't bother him anymore and he lurched forward, desperate to find and claim the source of that beautiful, beautiful scent.

In his daze he vaguely remembered the horrifying sex ed conversation his parents had given him when he had presented as an alpha.

"_It'll be hard to resist Rei, but if you smell an omega in heat you have to get away from there. At least until you're a bit older and can control yourself. Forcing yourself on an omega is wrong, remember that."_

_Rei turned to his father. "But what do they smell like?"_

_His father turned towards his mother with a knowing glint in his eye that completely went over his 10 year old head. "You'll just know."_

Rei quickly realized that what he was smelling was the exact thing his parents had warned him against over a year ago, the alluring scent of an omega in heat. He quickly plugged his nose, but the smell didn't fade. It was like it had become part of his very being. It was all he could see, all he could taste, all he could hear. It was entire world and he couldn't stop his feet from moving forward, closer to the nurse's office door where he knew the omega would be waiting. He was vaguely aware of his cock lengthening in his uniform pants as he prepared to take what was rightfully his.

"Ryugazaki-kun?"

Rei froze at the sound of his teacher's voice echoing down the hall.

_It's Mochizuki-sensei, _Rei thought. _Oh God he's an alpha, he's going to know what I was about to do! This is too embarrassing!_

Cheeks flaming and his mind temporarily distracted from the alluring scent coming through the office door, Rei quickly turned away from his teaching and ran as fast as he could, his lustful body protesting ever step he took away from that perfect scent. He ran until he reached the boys bathroom, panting heavily and his cock aching from how hard it was. He quickly ran into a stall and ripped his uniform pants down, gripping his cock with a shaky fist. It only took a few quick pulls before he was coming hard, his release splashing into the toilet in front of him as tears rolled down his face.

_I almost raped someone._

_I almost forced myself onto an omega in heat._

_I couldn't control my actions. I was a slave to my alpha desires._

_I'm despicable!_

It was that moment as Rei lurched out of his bathroom stall and scrubbed his hands raw in the sink, that he truly began to despise what he was. To him, all that fighting was just a grab for power, to attract the willing omegas. How could he be expected to keep an omega safe when he had just tried to take advantage of one?

Rei stared at his teary face in the mirror. His eyes were puffy and swollen while his skin was covered in unsightly red splotches.

_It's not beautiful._

_This insatiable lust and thirst for power is ugly and disgusting. I have no right to hold power over anyone. Why do alphas believe they can hold such a power? But I don't like the power that omegas hold over alphas either. They make us slaves to our desires._

It was on that day that Rei Ryugazaki began to hate the system of the world and fear both his instincts and the allure of the omegas.

He had gotten better at controlling himself around omegas, but he still treated them as something to be avoided. It was a lot easier now that the omegas he was around on a regular basis knew when they were going to go into heat and could plan ahead accordingly. Every now and again he would catch the alluring scent in passing, but it was much easier for him to ignore. Like today as he was walking to the Hazuki residence with Nagisa chattering animatedly beside him when a faint whiff of heat drifted his direction. It was strong enough to distract him, but not enough to keep him from realizing that his bubbly friend had gone silent beside him.

"Nagisa-kun? Is there something wrong?" he asked as he tried to force himself to ignore the smell permeating his nose.

The smaller teen looked mildly startled for a moment before the same smile as always lit up his features. "I'm fine Rei-chan. My lunch just gave me some problems for a minute."

"Are you going to be sick? Do you want me to run to the store really fast and pick up some medication?"

Nagisa chuckled a bit at the genuine concern in his friend's voice. "Of course not Rei-chan. Whatever it was passed. I'm okay now."

"Are you sure? I don't want you throwing up all over my math homework."

"Rei-chan is such a mother hen. You're worse than Mako-chan!"

Rei's face turned indignant. "Well excuse me for worrying about the wellbeing of my friend."

"Aww, Rei-chan is so sweet!"

The taller teen merely scoffed in response but a small smile graced his face nonetheless. He relaxed a little as the smell drifted away and the duo continued their walk in silence.

"Nagisa-kun I've explained this problem to you five separate times now. Just take the value of this here and plug it in right here. It's simple!"

"You're only saying that because numbers actually make sense to you! It's not easy!"

Rei shook his head and pushed his glasses up the bridge of his nose. "That's because you're not trying hard enough."

That earned him a punch in the shoulder from his companion who then sighed and threw his head on the kitchen table with a thunk. "Rei-chan is such a tyrant. Just do my homework for me," he whined, voice muffled from the table.

"Then you'll never learn and you'll continue to fail your tests Nagisa-kun."

"But math is so hard and you're so good at it Rei-chan!" Nagisa's head flew up and he started to paw at his friend, grinding his head against his shoulder. "I'll cheat off of you so I won't fail, just don't make me do anymore math!"

Rei sighed at Nagisa's antics, but patted his head anyway. "Why don't we take a break and we'll come back to math. You like history right? Let's work on that instead."

"Noooo! I don't want to do any more homework!" the blond wailed.

"Well then what do you want to do Nagisa-kun?"

"I don't know. My family is out for the evening so why don't you make me some dinner!"

"Why should I make the dinner I'm the guest!"

"Because I don't want to cook Rei-chan! Come on. You'll be sustaining the life of your absolute best friend!"

"I don't think you'll starve if you don't eat tonight," Rei replied, but he stood up anyway, detaching Nagisa from all the places he clung to before walking over to the fridge and pulling out the necessities for stir fry.

"Rei-chan is the best!" Nagisa yelled happily as he leaned back in his chair. "I'll have to take you as my wife someday."

"Like I'll ever be anyone's wife," the taller teen murmured as he began cooking. A few minutes passed before Rei noticed that his friend wasn't being his usual chatty self. He turned around to find Nagisa still leaned back only with his eyes closed. He was panting softly and appeared to be in a mild amount of pain. "What's wrong Nagisa-kun?"

The blond opened one eye before closing it again. "I don't feel too good Rei-chan. My stomach huuuuuurts."

Rei walked over and peered down at his friend before placing the back of his hand against the blond's forehead. "You are kind of warm. Why don't you go lay down and I'll bring you a plate once it's done."

Nagisa stood up slowly and thanked Rei before going to his room and shutting the door. Rei continued cooking and decided to search for some medication after he fed Nagisa. It wouldn't do for the blond to eat only to throw it up a few minutes late. _Though maybe it would be best to give Nagisa the medication beforehand then,_ Rei mused to himself while he pushed the vegetables and meat around in the skillet. Just as he decided that the meal was finished and turned off the stove, a faint drift of heat flooded into his nose again, only this time it was getting stronger rather than fading away. It was almost as though an omega was calmly walking down the street toward the Hazuki residence and Rei had thrown all the windows open. It was starting to get potent and Rei quickly covered his nose as he thought about what to do. If the omega was in fact outside then it would be best to go into Nagisa's room which was the furthest away from the street. Rei figured that this was the best course of action so with his nose still firmly covered he walked into quickly toward his friend's room.

Figuring that he was safe back here, Rei unplugged his nose only be hit with enough heat to make his mouth water. The potent smell invaded every cell in his body, urging him to seek out whatever beautiful creature was creating the intoxicating aroma. It was all around him and he couldn't tell which direction it was coming from. In a daze he threw open Nagisa's door and barged inside, mind whirring.

He almost fainted at the sight that greeted him. Nagisa was draped across his bed like a lewd model. His hand was hidden underneath the waistband of his uniform pants but it wasn't doing much of anything other than twitching every few seconds. Almost like the blond wanted to jerk off desperately, but didn't possess enough energy to do so. Instead all of his energy was directed toward his restless writhing. His body jerked and his face was ruddy and damp with sweat. Rei had never seen such a beautiful sight in all his life.

"Rei-chan…something's wrong..i-it hurts," Nagisa panted as he continued to writhe amongst the already soaked sheets. The taller teen recovered his nose quickly as the scent of Nagisa practically punched all the air out of him. He took in deep, struggling breaths threw his mouth, willing his body to move. He wanted so badly to run but every fiber of his being willed him to go to his friend and take him.

_Look at him Rei, he's in pain._

_He needs you to help him, you'd be an awful friend if you just left him here like this._

Rei knew he needed to leave and quick before he did something that both of them regretted. He remembered his father's words all those years ago telling him how awful it was for an alpha to take an omega against its will and that gave him the strength to take at least one step backward and closer to freedom.

"Wait no Rei-chan! Don't leave me!" Nagisa practically wailed as he stroked his cock once beneath his pants. "Please Rei-chan!"

At the sound of Nagisa's pained voice, pleading with him to stay, his resolve cracked a little bit more. "I have to go Nagisa. I can't be around you when you're like this."

_Think about how happy Haruka-senpai, Makoto-senpai, Rin-san, and Nitori-san are. An omega is the key to happiness._

Rei forced his body to turn around and take another step forward.

_If you don't take him, he'll find someone else who will. Do you really want to see Nagisa-kun with another alpha?_

Rei willed his thoughts to stop as he took another step forward. He was almost to the point where he could shut the door and relieve himself of some of the temptation when Nagisa's breathy voice reached his ears.

"Please fuck me Rei-chan. I-I'll do anything, just don't go. I need you Rei-chan. So so badly. Please."

The soft desperate voice of his friend appealed to every single one of his protective instincts. He wanted to end his pain and to comfort him in any way possible. However he wanted more than anything to claim and mate and mark up Nagisa so that everyone knew that the blond was his. He wanted their scents to mix and converge until you couldn't tell which was which. He wanted Nagisa and he thinks that he might want him forever.

Rei turned back around and examined the sight on the bed, struck again with how breathtaking Nagisa's splotchy face looked. Deciding that he would deal with what came later, he pulled his hands away from his face and took a long deep breath through his nose, reveling in the scent of his soon to be mate.

Nagisa smirked at the predatory light in Rei's eyes and opened his legs wider, inviting him in with his body language. The taller teen didn't need another hint and he quickly pounced on the blonde, pulling him in for a sloppy kiss. Their teeth clashed jarringly in their effort to get closer to one another and saliva dripped down their jaws. Rei quickly thrust his tongue into Nagisa's panting mouth, swallowing the resulting moan.

Rei's hands touched as much of Nagisa as he could reach. He left feather light touches down his arms, gripping his wrists hard enough to leave finger sized bruises when the blond bit his lip hard enough to draw blood. He quickly retaliated and ripped Nagisa's shirt off his pliant body, taking satisfaction in the sound of fabric tearing. He likely pinched his lover's nipples a bit too hard in his daze, but you couldn't tell from the resulting groan that poured loudly from the blond's mouth.

Rei pulled back, chuckling lightly at the way Nagisa followed his mouth, desperate for another kiss. He worked his way down, licking and kissing at the blond's jaw before reaching his neck. The teen laved at Nagisa's pulse point, loving the way it thrummed like a nervous humming bird from all the excitement. He sucked and bit harshly leaving a myriad of large bruises everywhere he could reach. He bit onto Nagisa's shoulder and lapped at the resulting blood as Nagisa screamed with pleasure, his mind too far gone to register anything close to pain.

Rei continued his trek downward, having to stop every once in a while to rut on the blond's shaking thigh just enough to take the edge off. Nagisa threaded his fingers through Rei's soft hair when he took a nipple into his mouth, sucking and nipping at it lovingly. He tried several times to pull the larger teen off of him and direct his mouth to more important places but Rei wouldn't move. He moaned around the bud in his mouth before moving to the other to give it the same treatment.

"Please Rei-chan. I can't take it anymore. Do something!" the blond wailed. He tugged at Rei's hair once more and this time he actually let go, moving to lick into Nagisa's mouth once more, easily taking dominance and exploring his lover's mouth like it was the last chance he got to do so.

He reached his hand down and pulled Nagisa's pants down just low enough to free his leaking cock. Keeping Nagisa's mouth occupied with his own, he gripped the blond's erection with a firm hand and stroked him quickly. Nagisa squirmed beneath him, moaning lewdly into his mouth as he came across Rei's fingers. The taller teen continued to stroke his cock leisurely until the blond was shivering with oversensitivity. He pulled away and stared at the beautiful sight beneath him before bringing his hand up to lick his fingers clean.

"Eww Rei-chan. You're disgusting."

"Mmm? But you taste so nice Nagisa-kun. Why would I want to waste it?"

Nagisa merely chuckled in response, but Rei knew he didn't have long until Nagisa would fall into another lust fueled daze. The scent of Nagisa was still potent in the air and Rei could feel the blond's cock quickly hardening once again against his stomach.

Before Nagisa could pull him into another kiss, Rei stripped off his shirt which was quickly followed by his pants and underwear. He finished stripping Nagisa as well before sitting back far enough to see the entire view. "God Nagisa. I've never seen anything even half as beautiful as you are right now."

"That's high praise coming from Rei-chan," Nagisa murmured breathily his gaze fixed on Rei's throbbing cock, the base already beginning to swell slightly with anticipation.

Rei merely hummed an affirmative noise in response before leaning down to suck and nip at the blond's left thigh. His scent was so much stronger down here and it drove Rei crazy with the urge to claim. He held back just long enough to insert a finger into Nagisa's slick entrance quickly followed by his tongue. The taste of Nagisa's heat exploded in Rei's mouth and it was all he could do not to pull back and push into the blond with as much strength as he could muster. He tried to keep his mind on track, quickly preparing the writhing body with his tongue and fingers, but his mind was too muddled to keep that up for long. Luckily it wasn't more than a minute before Nagisa could easily accommodate three of Rei's long fingers with ease. "Please Rei-chan, just hurry up and fuck me already," Nagisa whined and Rei was more than happy to oblige.

Unable to hold back any longer, Rei flipped the blond's limp body over onto his stomach and urged him to hold his ass high in the air. Nagisa complied with a low moan which transformed into a high pitched mewl as Rei slowly entered him. The smaller teen rocked his hips back as Rei drove in, desperate for that cock to be fully seated in him as quick as possible.

Nagisa whimpered when Rei paused to catch his breath, trying to keep from coming too quickly. "Ohmygod Rei-chan you have to move," he panted, eye watering slightly from the influx of sensation. Nagisa's body twitched with little aborted thrusts, trying to get the taller teen moving as quickly as possible. Rei groaned and draped his body across Nagisa's, one arm wrapped tight around his stomach and the other firmly placed on the bed to keep balance.

Trying not to focus too much on the tight heat of Nagisa's walls clenching around him, Rei began moving, unable to hold back any longer. He thrust in hard and fast, panting harshly as he drove Nagisa further up the bed, forcing him to grip the headboard. Anyone within the area would instantly know what was going on in the Hazuki household from the thick scent of Rei's alpha musk mixed with the smell of Nagisa's slick beginning to coat the back of his thighs as it dribbled down. Plus neither male was being exactly quiet either. Rei groaned with every other rapid thrust, the hand on Nagisa's hip digging in hard enough to leave bruises. He leaned forward and bit the blond's neck to hold him still, though his squirming did not cease.

Nagisa's fingers scrambled to find purchase against the headboard. His fingers dug marks into the word as he screamed from a particularly hard thrust to his prostate. "Rei-chan, there! Please ahhhhh more!"

Rei was happy to oblige, though his thrusts were becoming more erratic. He removed his teeth from the back of the blond's neck and lapped up the blood lovingly. He leaned down and took an earlobe into his mouth, nipping and sucking at it. He pulled back slightly and whispered filthy praise he didn't even know he was capable of saying into Nagisa's ear. "You're doing so good Nagisa-kun. Such a good slutty omega. Are you going to open up for me? Take my knot in that tight ass of yours?" Nagisa merely moaned, unable to do much more in the way of responding.

Rei could feel the base of his cock start to swell and he thrust in a few more times before it was impossible to pull out. Still he moved in tiny increments, forcing his cock in as deep as it would go as he gripped Nagisa's erection and jerked quickly. The blond squirmed and mewled as his body tensed before coming hard a few pulls from Rei's hand later. At the feel of already tight walls clamping around his swollen cock, Rei followed suit. He groaned, biting down on Nagisa's shoulder as he came hard, his knot swelling even further as it fought to hold all of Rei's cum inside the blond's pliant body.

Completely exhausted and wrung out, the arms holding up Nagisa's body collapsed and the two fell onto the bed, Nagisa grunting with Rei's weight and Rei unable to move where he was locked inside his lover. The taller teen pulled back, petting Nagisa's head soothingly as he maneuvered them onto their sides, Rei spooning Nagisa's back. The blond made a pained, scared sound when Rei moved a little too fast and the knot pulled uncomfortably against his rim, but the taller teen quickly soothed him with light kisses against the back of his head.

Nagisa snuggled closer to Rei and hummed in appreciation of the close warmth he provided. "How long before it goes down?" Nagisa asked, voice thick with impending sleep.

"I'm not sure," Rei replied. "I've never umm done this with anyone before."

"Good. I wouldn't want to have to kill anyone who touched my Rei-chan."

"I hardly think I'm _your_ Rei-chan," the other teen replied indignant.

"Of course you are! You're my Rei-chan and I'm your Nagisa-kun. That's the way the world works."

Nagisa's words reminded Rei of what he'd just done. The blond didn't sound angry now, but what if he did when the high from their actions wore off. He was pretty much stuck with Rei forever and all because Rei couldn't control himself when faced with an omega in heat.

"I didn't know you were an omega," Rei said finally trying to conceal the guilt in his voice. He didn't want to ruin the afterglow quite yet.

Nagisa yawned loudly before answering. "I didn't know either. I'd never presented as anything so everyone assumed I was a beta. Even my parents thought I was a beta. I'm glad it finally happened though. I had a constant feeling that I was in the wrong skin. But I feel better now."

Rei kissed the back of Nagisa's head once more before urging him to go to sleep. It didn't take long before the blond's soft snore filled the room and guilt began to bubble up in Rei's stomach as he thought about the consequences of his actions.

_What the hell have I just done?_


End file.
